Device for measuring gas leakage



Sept. 28, 1943- M. F." PETERS E1'- Al.

DEVICE FOR MEASURING GAS LEAKAGE Filed July 8, 1942 2 Sheets-Sheet 1 THQ mvr-:NroRs Melville F. Paters ATTO Y Sept. 28, 1943. M. F. PETERS E-wu.l

DEVICE FOR MEASURING GAS LEAKAGE Filed July 8, 1942 2 Sheets-Sheet 2 INVENToRs Melville F. Eier-5 Jahn. P. Eus'tnn B-Y #MEM Patented Sept. 28, 1943 Davies rola MEASURING GASLEAKAGE f Melville F. Peters, Beltsville,r ailaJeimi P. Besten, Y

Garrett Park,

, Applannen July s, 1942, serlellve. 450,200

9 claims. (cl. 'z3- 51) (Granted under the act ofM-archlB., '-188.3,as

' amended April 30, 1928; 370 0.- G. 757)r This application is a continuation in part of our copending application Serial No. 419,582, filed November 18, 1941 now abandoned. f

This invention relates to apparatus for measuring gas leakage and more particularly to apparatus formeasuring the gas leakage through and around ignition devices, especially those ignitionv devices which are to be used in internal combustion engines. y

It is a primary object of this invention to provide anl apparatus which will permit the rate of gas leakage of a spark plug torbe measured'with extreme precision when thesaid spark plug is installed in anl operatingl cylinder of` an internal combustion engine.

In carrying out the above objectmofI Athis invention, we prefer to utilize the deviceswhich normally serve to connect a detachable ignition lead of an internal .combustion engine to an installed and `operating spark plug and to modify the said devices to the extentV of providing va space enclosed by v said ,device with agas-tight sealing means Which includes a normally` open pressure releasing and sealing valve. A conduit is connectedL to the said device for the purpose of transtemperature may. be sultlcierltlyr high to cause` preignition inthe engine. This preignitionfur-` v temperatures andA pressure` conditions to which mitting pressure variations of thegas contained cator thus permitting the gas leakage Vrate to be measured by observing the ratel of increase' in pressure within said void space.` This typefof apparatus ,hasy an advantage over'that-disclosed in the parent application Serialv No. 419,582 in that the void space within the sealedv enclosure:L

factp that temperature dilierentials occurring 'in' the apparatus utilized are "small, consequently, the possibility of errors attributableto temperature variations is materially lessenedv and the condensation of liquid in the void space within which gas pressure measurements are obtained is effectively inhibited. 7'

within the void space to a suitable pressure indithe spark plug issubjec'ted, it'is desirablev to determine theleakage rate yiwtih the spark plug infstalled` in ran operatingy internal combustion lengine." The measured leakage rate should include the leakage ratearound the base of the. plug as `tlflelleakage rate throughthe plugstrucwell as ture.y It is alsdan object to provide "an instrument vvvln'ch will enable one toldetect' the rate of gas leakage throughthe spark plug .aswell as aroundthe screw joint, said instrument permitting these leakage measure-v mentsQtobetaken with the'plug operating, i.` e.

with t eplug installed" in an operating internal combustion` engine. f f f i s Y Notwithstanding the desirability of', having an instrumentvwhich can be used to'measure the rate oifleakage` through the`v structure of a spark plug Vas well asaroundnthescrewzjointconnection, it

- should also be evident l,that this leakage rate It isv well known that the gas leakage of an internal combustion'engine spark plug decreases the preignition rating of the spark plug causing its normal operating temperaturelto be increased.'` If the leakagek is great enough,'the"spark plug cannot be taken as a useful index of the leak-proof f quality oftheplug itself since a greater portion of the leakage.l rate rmeasured may be due to the screw joint tightness of the plug where it enters the engine, It-'is also,desirable,vtherefore, to have available an instrument which may be utilized to measure the leakage rate through the plug only; so that the leakage rate measured would be indicativeof theleak-proof quality of thelparticuutilization[serveA asta useful index of the plugs,

condition and 4inthe-second place, when used in conjunction "with lthey "apparatus which measures;

the total 4gas leakage, it is easy to determine what portionfof the Yleakagerateis dueto the screw.

joint tightness;

of this invention, therefore, y

Other objects, uses and advantages of this invention will become more apparent during the course of the following description taken in connection with the accompanying drawings, where- 1n:

Fig. 1 is an elevational View, partly in crosssection. `of a specific .type of dex/ice .in .which the total volume :of gas leakage through and .around a spark plug is measured and indicated by a` change in the height of the column of mercury in a capillary tube;

Fig. 2 is an elevational View, 'partly inc-roscsection. of a modification of the :species-.of this invention illustrated in Fig. 1 in which the :me-

chanical motion of a Sylphon bellows is used to measure the gas leakage volume;

Fig. 3 is an elevational view, partly in crosssection, of a further modification of the invention illustrated in Figs. 1 and 2, showinghow .the apparatus may be used to employ/:a low 'pressure gauge to register the pressure increase due to .the gasleakage within a nxed volume surrounding the spark plug, thus giving van .indication of the gas leakage rate.;

Fig. e is across-sectiona1 elevational view of .a modication illustrating .a preferred .embodiment of this invention wherein the mem'rber which serves normally to connect .the detachable ignition lead to a radio shielded spark plug is modified to permit gas 'leakage'measurementm Fig. .5 is an elevational View in cross-section of a further modication showing the invention applied to a member which serves to connect the detachable `ignition lead to an unshielded spar plug; and

Fig. 6 is an elevational view',partly in crosssection, of a further modiiication. l

` Before proceeding with a description of the various illustrated embodiments of this invention, it may be well to again emphasize the two types or species of instruments which we have disclosed for measuring the gas leakage. The first general type, originally described and claimed in a copending application Serial No. 419,582, filed November 18, 1941, now abandoned, of which this is a continuation in part, is manually applied to the spark plug and measures the `leakage through the plu-g itself and also the gas leakage around the screw joint Where the -plug enters the engine block or head. The second general type illustrated in Figs. 4, 5, and 6, `employs a device used to connect a detachable ignition lead to the spa-rk plug and modifies the device vso as to enable the gas pressure within a relatively small volume to 'be percisely measured. Any increase in the gas pressure as measured by this latter .device would serve as a useful index of the spark plugs condition. since the leakage of the gas producing this pressure increase must take place through the structure of the plug itself.

The preferred modification of this invention failing within the first of the aforementioned classifications. which permits detection of a very I minute quantity of gas leakage with extreme pre-- within the` spark .plug receiving cavity II.

manual pressure is applied to temporarily seal the plug I3 within the cavity II. A sealing ring I6, constructed of rubber or other similarly suitable gasket material, is located at the base of the cavity forming wall I7 and provides the gastight sealing joint with the portion I8 of the engine head .or block when .pressure is manually .applied at the handle M o'f the instrument. Within the barrel IG is a small gas-tight and liquid-tight bellows I9 which is adapted for longitudinal expansion when a slight pressure in- @crease is communicated to its interior 2U from Expansion of the bellows I9 displaces the liquid 2l from within the fluid filled reservoir 22 of the barrel Iil. "Ifhe overflow o-f the liquid indicated at 23 is forced into a capillary tube 24 which is connected to the liquid filled reservoir 22 at the `enel 25 `and which opens to the atmosphere at the other end .26. The barrel IU is inscribed with suitable gradui-itionsl 2l along thelength .of the capillary tube .24. These Agraduations .are calibrated so that the height of the `liquid within Athe capillary tube 'may be .interpreted in terms of pressure. By timing a set 'increase in the height of the displaced liquid 23 as it enters and fills the capillary tube 24K, an extremely accurate indication of the rate of gas leakage from and around the spark plug I3 maybe procured. Ignition current is supplied to the plug by a conventional spring type contact, 28 which is connected to an insulated conductor 29 passing through the wall SII of the cavity fI-I.

lte'ferring now tothe embodiment of our `invention shown in Fig. 2,'an indicator `rod 3i operable over a scale 2T is rigidly attached Vto the free surface -32 of the bellows I9 and replaces in function the liquid 21, the `reservoir 22, and the capillary tube 24 of Fig; 1 as the means for indicating on the scale 21 the ychanges inpressure in the cavity II 'This `speciesoyf the invention is more rugged than is that illustrated in Fig. 1 and is useful'for determining measurements of larger leakage,` although' withV less precision than the device shown in Fig. 1. 'Except for this difference Vconstruction Ithe remaining vfeatures of the modification in Fig. 2 are identical with those in Fig. "1. Hence, reference characters similar to those used 'in Fig. 1 indicate similar parts.

Referring now to the embodiment of this invention shown at Fig. f3, a pressure gauge 33 of the low pressure Bourdon type replaces in function the rod TSI and the scale 21 of the modification illustrated in Fig. 2 and the liquid'ZI, reservoir22 and the capillary ytube 24 of the modification illustrated in Fig. l, as the means for determining the`pressure differences within the cavity lI I, The differences in'operation between the devices illustrated in Figs. l and 2 from that shown in Fig. 3 is'that (in the former, differences in volumeare measured to indicate gas leakages, whereasin the latter increases in pressure due to gas leakages are sensitively indicated and precisely measured. In'Fig. 3 gas leakages from around the spark plug as Well as through the spark plug I3 enter the cavity II which is of a fixed volume and cause a gas pressure to be built up in this cavity. Increases in this gas pressure are indicated on the pressure gauge 33. In other respects the features of Fig. 3 are identical in con-struction with those of Fig. 2 and similar reference characters are employed to indicate similar parts, with the noted exception that in Fig.V 3 the barrelv I0 of the device is constructed of :an electrically conductive material and is in sulated from the engine block or head by means of `the dielectric gasketv material I6. In this case, the ignition `current supply conductor 29` may be attached directly to the barrel l to of these devices as there are spark plugs appliedl to a manifold of an engine undergoing test in a test line, whereby all of the spark plugs may be tested for gas leakage simultaneously. As soon as an engine has undergone appropriate test it could be rapidly moved rdown the line and another engine moved into the test stand.- In this manner all of the spark plugs may be rapidly tested .by` an apparatus involving a minimum number of operations and electrical connections.

Fig. 4 illustrates a further modification of this invention which is characterizedby the fact that it falls within the latter of the two general classifications set out above. The apparatus disclosed in this modification is adapted to accurately measure or indicate the gas leakage through a radio shielded spark plug I3 and includes the conventional elbow 4!) of the shielded spark plug ignition lead IH. Thedetachable ignition lead or cable 4l which preferably extends from the spark plug terminal to v the terminal of the manifold conductor leading from the magneto ina manner wellunderstood in the art and particularly disclosed and described in the United States patent to M. F. ,Peters et al. No. 2,164,591, is passed through the elbow so as to substantially fill the space enclosed thereby.Y One end of the elbow is threaded so as to receive the flanged nut 42 which is provided forthe purpose of securing the elbow to the metallic shielding tube 43. Thisv end of the elbow is Valso provided with a tapered circular recess M adapted to receive the conically` formed packing 45 of rubber or other suitable compositions. The packingis substantially the shape of a truncated conebut the portion adjacent the base thereof may have a short cylindrical extension. around the insulated cable M and is forced into the tapered recess 44 so that its inclined face abuts the inclined face of the recess 44. flanged end 45 of the shield tube 43 terminates adjacent the base of the packing 45^and is forced against the base of this packing when the flanged nut 42 is tightened on the threaded porrtion of the elbow 4i)- f The 4force thus applied to.

the flanged .end 46 of the tube 43 urges the inclined faces of the packing 45 against the conical seat and makes a gas-tight seal between the cable 1H and the edbow 40. For a more detailed description of the type of packing similar to that disclosed, reference may be had to the United States Patent No, 2,087,920-

. The spark plug end of the elbow has secured upon it the metallic member 47 having a iiange 48 engaged by the flange i9 onthe threaded nut 5f) which is adapted to be screwed on to the spark plug shield to hold the elbow tightly and securely thereto. Agasket 5l is interposed between the elbow and the shield to insure a gastight joint at this `end of the elbow. Threaded into the'member 41 is a tubular mounting 52 of insulating material having a centrally formed bore 53 through which` extends the insulated,

This. packing 45 is disposed Thev with a passageway 54 permitting easy escape or passage of thegas leakage through the spark rplug into the enclosed space formed by the elbow.4 A metallic washer 55 surrounds the conductor 4| ofthe insulated cable 4I so as to bear against.

the insulation. IThe disc 56 to vwhich aspring 51 is soldered is disposed within the bore 53 and bears against the .Washer 55 to make electricalv contact therewith.- The spring 51 acts to connect thel conductor 4I vwith the electrode of the.

The elbow 4i) is'also provided with a vent 6| toy atmosphere having a`valve'seat62 formed therewith. The operating stem 63 for the valve closure disc 64 has a compressional spring 65 associated therewith to retain the .closure disc B4 ina posi-,

tion displaced off the valve seat. A button 66 is secured to anend of the operating stem 63 so that upon ther application of a. ,manual force thereto the closure disc 6'4 will be firmly pressed-v against the seat, so, as tol seal the escape of gas from within the enclosure formed by said elbow.`

A second opening 61 is provided in this elbow 40 into which one end of anoililled' capillary tube 68 is sealed; the other end of this tube is connected to a lowpressure gas gauge v69 of the Bourdon type. The normally open vent lil` is necessarily provided to prevent excessive presf sures from being built up within the enclosure formed by the elbow 40. during the intervals when the leakage ratesare notbeingobserved. -In order to determine the rate of gas leakage the button 65 is held down manually and the-reading of the gauge 69 is noted. Consecutively timed readings of the gauge are also noted to deter- -mine the rate of increase in pressure which is an index of the gas-tight condition of the spark plug.

` Obviously, plugs' other ythan those. provided with a radioshield are subject to gas leakage. Consequently, the instrument or apparatus disclosed in Fig. 5 is provided forthe purpose of detecting the rate of gas leakage through the type of unshielded spark plug. .As illustrated, thef device consists` specifically of a cap 'llformed preferably of an insulating material Y such Vas Bakelitefor examp1e, A terminal 'Il Vis molded or threaded into this capA and one end is threaded to Areceive the nut vi3 bylmeans of which the ignitionV cable maybe secured thereto. The inner end of the terminal l1l has a spring 1.4 soldered thereto which is adapted to engage the vspark plug terminalin the manner illustrated. They base of the cap "Hl is providedv with a suitable elastic material 15 which is` congured to encircle'the plug 'I3 and .to hold the cap thereon and providesla gas-'tight seal' Yof'the `enclosure formed therewith: .-As illustrated, this elastic material 'l5 is cementedas` at3 to the Bakelite cap .'l. We dov not propose toybe limited to the particular` means of securing `the elastic materialv or forthat `matter tothe .type c f cap illustrated pose of this .invention by providing a suitable gas-tight enclosure,l of thespace formed thereby, as illustrated by Fig. 6. The cap 15,' as illustrated.:

cable 4I. .This mounting member 52 is providedf is also;V provided' with aiv normally open manually operated pressure release valve 1G which vents to atmosphere'and withv an oil lled capillary tube'- 7'1 which" is sealed to cap 10 and leads therefrom to' the Bourdon' typepressure gauge 18. The valve? T8 prevents excessive pressure from being built up within the enclosure dened by the cap 'If 'when measurements of the gas leakage rates are not being taken. In order to observe the gasleakage through the plug, it is only necessary tog manually closeI the valve 16 and' note the rate of increase Vpressure on the dial of the pressure gauge '18". Y 1

the'modicatio'n illustrated in Fig. 6, the cap F" has' a suitable ring gasket 80 located at the baseof the cap. 4The cap 1U is secured in place by the spring clip 8|k forcing the gasket` 8l) into g'asetight engagement with the plug i3. In other respects, Figs'. @and 6 are similar and both are similar to Fig'. 4 asY regards the construction of theN valve and similar reference numerals have been used to' indicate their corresponding parts.

It shouldbeunderstood that the forms of our invention shown and described herein are to be as preferred examples and it is understood that yvarious changes in the shape, size and arrangements ci parts mayv be `resorted to without departing fromthe 4spirit of our invention or the scope @fthe subjoined claims.v l

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes 'withoutn the payment of any royalties thereon o r therefor.

We claim: Y

l.. Afr apparatus `for determining the rate of gas leakage through a spark plug when it is installed in a cylinder of an operating internal combustion engine, comprising in combination a means for enclosing at least a portion of said spark plug protruding exteriorly of said cylinder within a gasetight enclosure and means for detscting changes in the gas pressure within said enclosure, saidenclosing means including means for applying an ignition potential to the electrode or" said sparkplug without permitting gas leakage between said enclosure and the atmospheie, whereby the gas leakage rate may be determined during the normal operation of said spark plug by observing the rate of change indicated by said gas pressure detecting means.

2. An apparatus for determining the rate of gas leakage from a combustion chamber of an operating internal combustion engine through its installed spark plug and around the tted portion thereof where it extends into the interior of said combustion chamber, comprising in combination means for completely enclosing all portions of the spark plugwhicli extend exteriorly of said com'- bustion chamber, said enclosing means contacting the outer wall of said combustion chamber at the base of said spark plug where it enters the engine, and meansfor detecting changes in the gas pressure within said enclosure, said enclosing means including means for applying an ignition potential to the electrode of said spark plug without permitting gas leakagev from said enclosure, whereby the rate of 'gas leakage may be determined during the normal operation of said spark plug by observing the rate of change in gas pressure indicated by said pressure detecting means.

3. In a spark plug g'as leakage measuring device, a barrel having a plug receiving cavity in the 'end thereof, means forming agas-tight seal around the edge ofl said i cavity, means for' de tect'ing changes in the gas pressure within said cavity,v and means for supplying an ignition current to -an operating spark plug enclosed within the said spark plug receiving cavity without permitting any gas leakage thereabout.

4. In a spark plug gas leakage measuring device, a cylindrical barrel, a handle at an end thereof, a plug receiving cavity at the other end, means forming a gas-tight seal around the edge of said plug receiving cavity when a manual force is applied to said handle, a gas-tight selfrestoring bellows having its interior connected to the said cavity so that gas pressure within said cavity is transmitted to the interior of said bellows causing an expansion or contraction thereof, visible means for indicating the expansion or contraction of said bellows, and means for supplying an ignition current to the spark plug enclosed Within said spark plug receiving cavity without permitting gas leakage thereabout.

5. An apparatus for determining the rate of gas Vleakage from a combustion chamber of an operating internal combustion engine through its installed spark plug and around the tted portion thereof where it extends into the interior of said combustion chamber, comprising a member containing a cavity adapted to receive the exterior-ly protruding portion of an installed and operating spark plug when the member is placed over the spark plug installed in the combustion chamber from which gas 'leakage measurements are to be made, means forming Aa gas-tight seal between the surface edges of the walls of said member deiining the cavity and the exterior surface of said combustion chamber when a force is manually applied to said member, means for detecting a change in pressure within said gastight cavity and means for applying ignition potential to the spark plug within said cavity without permitting gas leakage thereabout, whereby the rate of gas leakage may be determined during the normal operation of said spark plug' by observing the rate of change in gas pressure detected by said pressure detecting means.

6. In a spark plug leakage measuring device, comprising in combination a cylindrical barrel containing a Acentral chamber and a plug receiving cavity at an end thereof, a gas-tight seal forming gasket of plastic material distributed around the edge of said plug receiving cavity, a liquid completely filling the said central chamber, a iiuid-tight diaphragm interposed between the said plug receiving cavity and the said liquid filled central chamber so that gas pressure on the cavity side of the said diaphragm will cause the same to expand and displace liquid from the said liquid filled chamber, an outwardly visible graduated capillary tube one end of which 1s a continuation of the said liquid filled chamber and the other end of which is open to the atmosphere, so that displaced liquid will enter the interior of the said capillary tube and aord an exact measure of the displaced liquid, and an insulated electrical conductor with a spring spark plug contact sealed into the cylindrical barrel of the plug receiving cavity end thereof for supplying an ignition current to a spark plug under test.

7. An apparatus for determining the rate of gas leakage from a combustion chamber of an operating internal combustion'engine through its installed andoperating radio shielded spark plug.

comprising in combination a radio shielding elbow defining an enclosure, a ,conductor in said elbow insulated from the metallic sides thereof, one end being adapted to connect with the eleotrede of a spark plug, means connecting the end of said elbow containing said end of said conductor with the spark plug radio shield, so as to form a gas-tight connection therewith,V and means forming a gas-tight seal at the other end of said elbow between said conductor and said elbow whereby said enclosure will be rendered gas-tight, a normally open manually operated pressure sealing and releasing valve connected to said elbow to provide at all times other than during gas leakage rate measurements a vent Vto atmosphere of the gas leakage through said spark plug and means for detecting the changes in gas pressure within said enclosure, whereby the rate of gas leakage through the plug may be determined during the normal operation of said spark o plug by manually closing said valve and observing the rate of change in gas pressure indicated by said gas pressure detecting means.

8, An apparatus for determining the rate of gas leakage from a combustion chamber of an operating internal combustion engine through an installed and operating spark plug comprising a cap forming an enclosure with said spark plug, means carried by said cap to make contact between theelectrode of said spark plug and an ignition supply cable, means securing said cap to said spark plug for rendering said enclosure gas-tight, a normally open manually operated pressure sealing and releasing valve connected to said cap to provide at all times other than during gas leakage rate measurements a vent to atmosphere of the gas leakage through the spark plug and means for detecting the changes in gas pressure within said enclosure, whereby the rate of gas leakage through the spark plug may be determined during the normal operation of said spark plug by manually closing said valve and observing the rate of change in gas pressure indicated by the gas pressure detecting means.

9. An apparatus for determining the rate of gas leakage from a combustion chamber of an operating internal combustion engine through an installed and operating radio shielded spark plug comprising in combination, an ignition cable shielding means forming an enclosure for `connecting said ignition cable to .said spark plug, sealing means for rendering said enclosure gastight, saidV sealing means including a normally open manually operated pressure sealing and releasing valve and means for detecting changes in pressure within said gas-tight enclosure, wheree by the rate of gas leakage through the plug may be determined during normal operation of said spark plug by manually closing said valve and observing the change in gas pressure as detected by said gas pressure measurements.

` MELVIL-LE F. PETERS. JOHN P. BOSTON. 

